1. Field of the Invention
The present invention relates to a marker detecting apparatus which detects marker signals of a time code signal, and to a radio-controlled timepiece including the marker detecting apparatus.
2. Description of the Related Art
Conventionally, there is known a radio-controlled timepiece which decodes a time code signal of a received standard radio wave (standard time and frequency signal) so as to obtain time information. Furthermore, there are known various technologies by which a time code signal can be accurately decoded even under a poor reception environment.
For example, Japanese Patent Application Laid-open Publication No. 2006-071318 (which corresponds to US 2006/0050824 A1) discloses a technology by which a time code signal is sampled at a prescribed frequency while the sampling data is subjected to convolutional waveform addition on a one-minute cycle, and the decoding process is performed based on the data.
Furthermore, Japanese Patent Application Laid-open Publication No. 2005-249632 (which corresponds to US 2005/0195690 A1) discloses a technology by which a time code signal is sampled at 50 ms intervals so as to be stored, and it is judged which code the sampling data shows by calculating a matching score between the sampling data and a temperate pattern.
For example, in order to find a minute synchronization point for x min. 00 sec. (the “x” is an arbitrary value) of a time code signal, it is necessary to detect marker signals which represent positions in a frame of the time code signal. The marker signals are always disposed at positions of 0 sec., 9 sec., 19 sec., 29 sec., 39 sec., 49 sec., and 59 sec. in a frame of a time code signal, respectively. Therefore, it is expected that the influence of noise can be reduced, and hence, the marker signals can be accurately detected, by subjecting the sampling data of a plurality of frames of the time code signal to the convolutional waveform addition on a one-minute cycle, and determining the marker signals based on the data as disclosed in Japanese Patent Application Laid-open Publication No. 2006-071318.
However, storing all the sampling data of the time code signal as it is and/or performing the waveform addition by using all the sampling data require a very large memory capacity, and also increase a load of an arithmetic process.
The present invention provides a marker detecting apparatus and a radio-controlled timepiece which can accurately detect the marker signals even under a poor reception environment, and also can detect the marker signals with a relatively small memory capacity and a light load.